Sal Heartwood Borer in Madhya Pradesh

Abstract

Shorea robusta, which is one of the most important timber species of India, yields about 2.5lakh m³ of timber and 3lakh m³ of firewood. A heartwood borer, Hoplocerambyx spinicornis, often damages it. Its beetles emerge soon after a few showers of monsoon rains from the third week of June to the end of August. They attract to the odour of freshly cut bast and sapwood of sal. Soon after mating, the beetle oviposit white, cream coloured eggs in cracks on the bark. After 3-7 days of egg period, the hatching takes place. The freshly hatched grubs bore the bark and reach to the sapwood, where they form tunnels. After feeding the sapwood, the grub move to heartwood where they form a wider pupal chamber, the grubs start pupation from December onwards, develop to immature beetles between April to May and emerge out from middle June onwards during monsoon. The male has long antennae than their body while the female has short antennae. The incidence of attacked sal trees due to heartwood borer lasts upto 24.33 per cent during epidemics. Continuous favourable climatic conditions, vicinity of human and herbivore population, physiological properties of sal trees to insect borer, quantitative and qualitative changes in host trees, natural enemies of sal borer and weaken of defensive system of sal trees are recorded as probable factors responsible for sal borer epidemics. Borer killed more than 26lakhs of sal trees during recent sal borer epidemics between 1996-02. Felling of these attacked sal trees in dense sal forests opened the canopy and resulted an average regeneration upto 4.18 saplings per square meter of sal and other miscellaneous species as compared to 1.95 saplings per square meter in unfilled sal areas. In human inhabitant areas however, it is reported to be comparatively low. Besides existing preventive and remedial control measures, the authors have advocated spraying of 0.05% endosulfan 3.5 ml insecticide per litre of water of 0.05 per cent chlorpyriphos (10 ml insecticide/litre) on stored borer attacked sal stacks and then covering them with polythene sheets before monsoon in June to kill the beetles emerging from sal logs. Further research need on sal heartwood borer, its out break and management are also mentioned.